This document describes how to build a multi-tenant Rails application that can handle multiple domains and languages. It introduces a Website model to store domain and language configuration and a WebsiteSwitcher middleware that sets the current website based on the domain. The middleware initializes a WebsiteSwitcher using the request host, finds the corresponding Website, and sets it as the current website along with its language before the request is passed to the application. This allows a single Rails app to serve different content and languages depending on the domain or host.

1. Multi tenant/lang
application
Simon Courtois - @happynoff

2. Multi-tenant you say?

3. mywebsite.com
otherwebsite.com
and-another.com
APP

4. APP
middleware
switcher
Website

5. Website
domain
lang
class Website < ActiveRecord::Base
def self.current
Thread.current[:website]
end
!
def self.current=(website)
Thread.current[:website] = website
end
end
Website.current = Website.first
!
Website.current
# => #<Website domain=“mywebsite.com" lang="en">

6. APP
middleware
switcher
✔ Website
Website

7. switcher
class WebsiteSwitcher
attr_reader :domain, :host, :website
!
!
!
!
def initialize(host)
@host = host.downcase.chomp('.')
end
def domain
@domain ||=
ActionDispatch::Http::URL.extract_domain(host)
end
def website
@website ||= Website.where(domain: domain).first ||
Website.where(domain: 'mywebsite.com')
end
def switch!
Website.current = website
I18n.locale = website.lang
end
end
WebsiteSwitcher.new('www.mywebsite.com').switch!

8. APP
middleware
✔ switcher
switcher
✔ Website

9. middleware
require 'website_switcher'
!
class WebsiteSwitcherMiddleware
def initialize(app)
@app = app
end
!
!
!
def call(env)
request = Rack::Request.new(env)
WebsiteSwitcher.new(request.host).switch!
@app.call(env)
end
end

10. APP
✔ middleware
middleware
✔ switcher
✔ Website

11. require 'middlewares/website_switcher_middleware'
!
APP
module AwesomeApp
class Application < Rails::Application
# ...
!
config.middleware.use WebsiteSwitcherMiddleware
end
end

12. ✔ APP
APP
✔ middleware
✔ switcher
✔ Website

13. Questions
?

14. Thank you
Simon Courtois - @happynoff